Missing 3-4 gallons.

[Cuprum-74]

So after almost 10 years of driving the duster and tolerating the gauge going empty & putting in only 10-11 gallons. I figured it's time to find out what is really going on.

So after a few experiments that usually resulted in running out of fuel & using the "1 gal trunk reserve tank" (spare gas can) to get to the next gas station.
I've been running out of gas on average at around 12.5 gallons. If I fill the gas tank to the point that gas is almost coming out of the filler neck then I can get about 13 gallons.
I'm getting roughly 10.5 to almost 12 mpg around town, and about 15 to over 17 on the freeway cruising at 70 mph w/ 3.21 gears. (Also depends if I'm drivin' granny or drivin' angry)
Moderate build 360 with a Non-LU A999.

So, it looks like I'm going to drop the tank and have a look see. The previous owner of the duster said that he bought and installed the new tank & sender.
So looking back I should've done a quick inspection to make sure the sender is indeed correct or not of the cheap flavor.
But oh well, but I'm really curious to see what I'll find.
Updates (& pictures) to come!

 

[Craig Burriss]

Could be as simple as a ventilation issue.

 

[hunt2elk]

Before you go through the hassle of dropping the tank. Pull the sending unit and then make sure the pickup is resting on the bottom of the tank. I would bet it is not and a little bending of the tube will fix the problem.

 

[Cuprum-74]

Could be as simple as a ventilation issue.

Earlier I thought that was the case as well, So I checked it and it is working. (Trying to figure out the easy stuff first).

 

[Dana67Dart]

Do you have an 18 or 16 gallon tank?

My money is on the pickup being too far above the tank floor.

There was a TSB for another Mopar where the factory pickup was too high and bending it downward was the OEM solution.

Be sure you don't bend it above the attachment of the rheostat as that will change the accuracy of the sender.

Also a hole in the pickup tube can do the same.

Maybe even the pickup filter missing could do the same.

The stance of your car could have an effect if it was way high in the air the pickup might be in air with a few gallons still in the tank.


I have the same issue I have 2 gallons in the tank when I run out of gas.

I just tend to fill up when I'm at 1/4 tank.

 

[72bluNblu]

You'll never get every drop or even every gallon out of one of these tanks. Just the nature of the pickup and tank will keep you from getting it all. You should be able to do better than 3 gallons, but I would say 1- 1.5 gallons is just par for the course. And yeah, the rake on the car could make a pretty significant difference, especially if the pick up isn't perfect.

You might be able to get closer if you're sitting in your driveway with the car level and the pickup sitting perfectly on the floor of the tank, but when you're driving everything is moving and sloshing and a little bit of air will sputter the engine.

The reproduction tanks are 16 gallons. Maybe there really were 18 gallon factory tanks, but, pretty much all the ones I've seen were 16.

I wouldn't drop the tank unless I knew it was full of junk. Check the sender to make sure the pickup is as low as it can get, and while the sender is out grab a mirror or something and have a look in the tank. If something in the tank is causing you to be several gallons shy of 16 it should be pretty obvious.